Enhanced Ising superconductivity in a unicompositional bulk 4Hb-TaS2 superlattice via pressure

Ising superconductors, known for their exceptionally high in-plane upper critical magnetic field ( $${{{\rm{\mu }}}₀H}_{{\rm{c}}2}^\parallel $$ ) beyond the Pauli limit, have so far been explored mainly in two-dimensional limit systems and molecularly intercalated bulk materials based on transition metal dichalcogenides. By exploiting the high pressure approach, we simultaneously optimize the superconducting transition temperature ( $${T}_{{\rm{c}}}$$ ) and $${{{\rm{\mu }}}₀H}_{{\rm{c}}2}^\parallel $$ in a bulk 4Hb-TaS2 Ising superconductor. The pressure-optimized Ising superconductivity of 4Hb-TaS2 exhibits drastically enhanced $${{{\rm{\mu }}}₀H}_{{\rm{c}}2}^\parallel $$ that is comparable to the performance of three-layer TaS2, while also with a record-high $${T}_{{\rm{c}}}$$ surpassing all the TaS2-based systems reported so far. Combined in-situ high-pressure X-ray diffraction, Hall-effect measurements, and theoretical calculations, we reveal that the dome-shaped $${T}_{{\rm{c}}}(P)$$ behavior of 4Hb-TaS2 arises from competition between superconductivity in the H-layers and charge density wave (CDW) orders in the T and H layers. Simultaneously, the dome-like response of $${{{\rm{\mu }}}₀H}_{{\rm{c}}2}^\parallel $$ on pressure is governed by synergistic effects of interlayer coupling and spin-orbital coupling. These central findings provide a practical route to achieving record-high functionalities of Ising superconductivity with superior application potentials.